1. Field of the Invention
This invention relates generally to disk drive systems and more particularly to a disk drive having an air bearing spindle.
2. Description of the Prior Art
Disk drives store data as magnetic transition marks on disk surfaces. The data is read by first moving a magnetic head to the desired track of the disk, then reading data as the disk rotates. In order to achieve faster access to the data (shorter latency time) it is necessary to increase the rotational speed of the disk spindle. However, traditional disk drive ball bearing spindles can only operate at rotational speeds less than approximately 8000 RPM for reasonable lifetimes. The ball bearings are not perfectly round and the ball bearing race within which they sit can deform slightly. In addition, the ball bearings are vibration generators. These problems cause the spindle axis to randomly or non-repeatably run out. This random fluctuation in the orientation and position of the rotational axis of the spindle effectively reduces both circumferential bit density and radial track density that may be achieved and hence the total data density of the disk drive.
One solution to this problem is to use air bearing spindles. Some examples of air bearing spindles include U.S. Pat. No. 3,751,044 issued Aug. 7, 1973; U.S. Pat. No. 4,087,095 issued May 2, 1978; U.S. Pat. No. 4,366,993 issued Jan. 4, 1983; U.S. Pat. No. 4,547,081 issued Oct. 15, 1985; U.S. Pat. No. 4,656,545 issued Apr. 7, 1987; U.S. Pat. No. 4,797,009 issued Jan. 10, 1989; U.S. Pat. No. 4,856,918 issued Aug. 15, 1989; German patent application 3819310 published Dec. 14, 1989; Japanese patent application 01-167495 published Jul. 3, 1989; Japanese patent application 61-236068 published Oct. 21, 1986; and Japanese patent application 61-38217 published Feb. 24, 1986.
A number of problems have been encountered with implementing air bearing spindles in disk drives. Air pumps may be used to provide a supply of pressurized air. Such pumps increase the complexity and cost of the system. Self-generating air bearings have been used, but they have proved inadequate in providing a sufficient thrust bearing at higher loads. Alignment between the thrust and axial bearings is also very difficult. Air flow from the air bearings may contaminate the recorded disks. What is needed is a practical air bearing spindle for a disk drive which is able to operate at high rotational speeds.